Incandescent-lamp mount



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Patented Dec. 17, 1929' UNITED STATES PATENT OFFICE PERCY A. CAMPBELL, OF EAST CLEVELAND, OHIO, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION-OF NEW YORK INCANDESCENT-LAMP MOUN '1 Application filed December 14, 1927. Serial No. 240,032.

adapted to be heated to incandescence. More particularly my invention relates to the electrical connections between a coiled filament and its supports and to methods of manufacture thereof. My invention is particularly adapted to the mounting of coiled filaments for gas-filled lamps such as disclosed in Langmuir Patent No. 1,180,159, issued April 18, 1916. The object of my invention is to produce a joint between its filament and support which .will be strong and minimize a tendency to are and which, moreover, may be conveniently manufactured at comparatively low The practice has been to coil tungsten and like refractory metal filaments on copper,

brass, nickel and other comparatively nonrefractory mandrel wires. It has been the practice to afterwards dissolve out the mandrel completely by a suitable re-agent, usually an acid, which does not affect the tungsten. A mount has then been made by welding or otherwise uniting the ends of thefilament to supports usually of nickel. According to my invention the ends of the coiled filament containing. short lengths of a mandrel composed of the non-refractory metals are united to the filament support. This produces a much more secure joint and on account of the larger cross section, the temperature durin the operation of the lamp is not nearly as hlgh thereby reducing the percentages of failures of filaments at the joint. Moreover the avoidance of high temperature reduces the tendency to are which is a trouble which frequently occurs between the leads in gas-filled lamps. Another feature of my invention is the method of manufacture. I

prising a filament and support therefor embodylng my invention; Fig. 2 is a similar new of another form of electric incandescent lamp and filament; Fig. 3 is a fragmentary elevation on an enlarged scale showing the connection between the filament and its support; Fig. 4 is a similar view of another form of filament and support; and Fig. 5 is aperspective View on an enlarged scale of a portion of a double coiled filament and its mandrels.

The incandescent electric lamps shown in Figs. 1 and 2 each comprise the usual bulb 10, base 11 and stem 12 in which are sealed the leading-in conductors 1314. The conductive supports 1516 project within the lamp and at their inner ends are connected to the filament which is su ported thereby and by the anchors 17 18 an 19 projecting from the glass rod 20 forming part of the stem 12. As shown in Fi 3, the filament 21, ordinarily of tungsten, is first coiled upon a mandrel 22. The mandrel containing the coiled filament is then coiled upon a somewhat larger mandrel 23, and after completion, the coiled coil is then mounted upon the conductive supports 1516. The joint between the said refractory metal. In Fig. 4' another form of filament is shown which is of an inverted U- shape and like the form shfiwn in Fig. 3, has theshort mandrel at its env s.

The method which I prefer to follow in the manufacture of lamps of this character is to coil the filaments on the full length of mandrel wire and then dissolve out a portion of the mandrel by an acid mixture such as four arts nitric acid to one part sulphuricacid or y any other solvent which will not affect the tungsten or other filament wire.

What I claim as new and desire to secure by Letters Patent of the United States, is: 1. In an electric incandescent lamp or similar device, the combination of a conductive support and a coiled filament having therein at its end for a portion of its length a mandrel composed of non-refractory metal united to said support.

5 2. In an electric incandescent lamp or similar device, the combination of a pair of conductive supports and a coiled coil filament of refractory metal containing at each end thereof portions of mandrels composed of non-refractory metal.

3. The method of manufacturing filaments for electric incandescent lamps and similar articles which comprises the coiling of a refractory metal filament on a mandrel of nonrefractory metal and then dissolving out the mandrel from an intermediate portion of said filament leaving a section of said mandrel at each end.

4. The method of manufacturing electric incandescent lamps which consists in coiling a refractory metal filament on a non-refractory mandrel, dissolving out a portion of said mandrel from the intermediate portion of said filament, leaving sections of said mandrel at the endsof said filament and then uniting said ends to conductive filament supports to constitute the mount.

In witness whereof, I have hereto set my hand this 12th day of December, 1927.

0 PERCY A. CAMPBELL. 

